1. Field of the Invention
The present invention relates to a lens-fitted photo film unit having an IC (integrated circuit). More particularly, the present invention relates to a lens-fitted photo film unit in which information of various kinds is written to a memory IC incorporated therein.
2. Description Related to the Prior Art
A lens-fitted photo film unit is pre-loaded with unexposed photo film, and includes a mechanism disposed in a photo film housing for taking an exposures. A flash built-in type of lens-fitted photo film unit includes a flash device constituted by a flash discharge tube, a flash circuit or charger circuit, and a dry battery. This type is convenient for use in taking exposures with flash light, mainly for scenes at night, indoors, or in the dark.
There are systems suggested in U.S. Pat. No. 4,443,077 (corresponding to JP-A 56-154720) and JP-A 2-217829 in which a memory IC or semiconductor memory is incorporated in a photo film cassette or cartridge, and in which exposure-taking information obtained by a camera upon an exposure is written to the memory IC to be used in a photo laboratory or by users.
Examples of exposure-taking information are exposure data, print format data, date data and caption data. The exposure data represents information of a shutter speed, an aperture stop, and existence of emission of flash light. The print format data represents any of printing aspect ratios of a standard size, a panoramic size and an L-size. If the camera has a structure suggested by JP-A 54-26721 for designating a trimming range, the print format data may represents the trimming range. The date data represents a date of taking an exposure. The caption data represents a sequence of letters input by a user of the camera with its pushbuttons or the like for recording a caption or phrase.
The exposure-taking information is read in the course of printing operation in a photo laboratory. For example the exposure data is used in control of exposure in the printing operation. The print format data is used for automatic determination of printing magnification, and a changeover of a negative photo film mask and a paper mask. It is possible to obtain photographic prints with an format or magnification desired by a user even if all exposures are taken at one equal frame format by the camera.
U.S. Ser. No. 08/784,259 (corresponding to JP-A 9-211680) suggests a lens-fitted photo film unit in which an memory IC is incorporated in its photo film housing or a photo film cassette pre-loaded therein. Exposure-taking information is written to the memory IC. A write control IC and the memory IC are supplied with power by a battery associated with a flash device. Upon the finish of taking each exposure, the write control IC writes the exposure-taking information to the memory IC.
If the flash circuit of the flash unit operates while the exposure-taking information is written, a comparatively great current flows in the flash circuit. The voltage of the battery drops in a temporary manner, to cause errors in operation of the write control IC or the memory IC. It is likely that no exposure-taking information is written to the memory IC, or that data different from the correct exposure-taking information is written.
In view of the foregoing problems, an object of the present invention is to provide a lens-fitted photo film unit in which information of various kinds is written to a built-in memory IC without errors.
Another object of the present invention is to provide a lens-fitted photo film unit in which charging of a main capacitor of a flash device can be stopped with a simply constructed circuit.
Still another object of the present invention is to provide a lens-fitted photo film unit in which a write control circuit for use with a memory IC can be prevented from erroneously operating when a flash device is charged or operated for emitting flash light.
In order to achieve the above and other objects and advantages of this invention, a lens-fitted photo film unit includes a photo film housing, a photo film roll chamber formed in the photo film housing and pre-loaded with photo film in a roll form, and a cassette holder chamber, formed in the photo film housing, for incorporating a photo film cassette, to wind the photo film therein after being exposed, the photo film housing incorporating a flash-emission main capacitor, a flash discharge tube and a flash circuit, the main capacitor storing charge by a charging operation, the flash discharge tube emitting flash light by a discharging operation of the charge, and the flash circuit controlling the main capacitor and the flash discharge tube for effecting the charging operation and the discharging operation. A memory IC is incorporated in the photo film housing or the photo film cassette. A write control IC is incorporated in the photo film housing, for writing information to the memory IC, and for inhibiting the flash circuit from effecting the charging operation at least while the information is written. A battery supplies the flash circuit, the write control IC, and the memory IC with power.
The write control IC writes the information in association with taking of one exposure.
In a preferred embodiment, an information writer is disposed in the write control IC incorporated in the photo film housing, for writing information to the memory IC. A charge control signal generator is disposed in the write control IC, for supplying the flash circuit with an inhibit signal, to inhibit the flash circuit from effecting the charging operation. A controller is disposed in the write control IC, for controlling the information writer and the charge control signal generator, to cause the information writer to operate while the flash circuit is inhibited from effecting the charging operation, whereby a power source voltage of the battery is prevented from dropping while the information is written.
Furthermore a shutter mechanism is incorporated in the photo film housing, for taking an exposure on the photo film. An exposure detector unit detects operation of the shutter mechanism for one time, to generate a detection signal, wherein the controller causes the information writer to operate in response to the detection signal.
The flash circuit includes a charger switch, operable externally, for generating a charging signal. An oscillation transistor is connected with the main capacitor, having a base connected with the charger switch, turned on by the charging signal, for charging the main capacitor, the base of the oscillation transistor being connected further with the charge control signal generator, the oscillation transistor being forcibly turned off by the inhibit signal.
A potential of the charge control signal generator in generation of the inhibit signal is lower than a potential of the charger switch in generation of the charge signal.
Consequently information of various kinds can be written to the built-in memory IC without errors.
In a preferred embodiment, a voltage detector detects a reach of a charged voltage of the main capacitor to a predetermined voltage, to generate a detection signal. The controller causes the charge control signal generator to generate the inhibit signal in accordance with the detection signal.
The voltage detector includes a first circuit connected in parallel with the main capacitor, a detection current occurring to flow in the first circuit in response to application of the predetermined voltage thereto. A switching circuit is turned on in response to the detection current from the first circuit, for generating the detection signal.
Consequently the charging of the main capacitor of the flash device can be stopped with the simply constructed circuit.
In another preferred embodiment, a shutter mechanism is incorporated in the photo film housing, for taking an exposure on the photo film. A trigger switch is disposed in the flash circuit, turned on by the shutter mechanism upon operation of the shutter mechanism, for applying a trigger voltage to the flash discharge tube, to trigger the discharging operation. A signal generator, having a semiconductor switching element, generates detection signal in response to turning on of the trigger switch, wherein the controller responsively causes the information writer to operate.
In still another preferred embodiment, a filter circuit is connected between the battery and the write control IC, for absorbing electric noises created therebetween, to prevent the write control IC from erroneous operation during the charging operation and the discharging operation.
Consequently a write control circuit for use with the memory IC can be prevented from erroneously operating when the flash device is charged or operated for emitting flash light.